Catalysis and catalytic systems



Sept. 8, 1959 KATAsHl olTA ETAL 2,903,404

cATALYsIs AND CATALYTIC SYSTEMS Filed oct. 4. 195e \sEPA/?Aron Caf. Res/due N f q JOU/70S Solvent For Polymers erating conditions as may be required to Patented Sept. 8, 1959 CATALYSIS AND CATALYTIC'SYS'IEMS Katashi Oita, Hammond, and Thomas D. Nevitt, Crown Point, Ind.,.assignors to Standard Oil Company, Chicago, lll., a corporation of Indiana Application October 4, 1956, Serial No. 613,888

12 Claims. (Cl. 2045-462) This inveiition'relates to novel catalytic systems and processes for the .preparation of normally solid polymers Vof thermoplastic nature from charging stocks comprising essentially a normally gaseous n-alkene, especially ethylene. ,The present invention provides novel and efcient processes for the homoor hetero-polymerization of ethylene or other normally gaseous n-alkenes to proextremely broad temperature range extending from about ,--100 C. up to about 250 C. The rate of ionizing radiation'dosage can be varied over a broad range, for

f example, from l to 100 kilo REP per minute or even more, provided that ultimately the polymerization charging stock is subjected to a total dose within the range of 104 to l0'1 1REP per gram of `olefin contained in the charging stock.

Ethylene has previously been polymerized by the use of ionizing radiations, alone or with so-called sensitizers such as alcohols, ethers, etc. (British Patent 714,843 of G. D. Buckley and Leslie Seed; l. G. Lewis et al., Chem.

Eug. Progress 50, 249-255, May 1954). However, the prior processes known to us have suered certain dis- ,advantages .has led to polyethylenes having a maximum density of f40.953 at about room temperature and the rates of poly- Thus, the use of gamma radiation alone `merization were relatively low. The use of organoduce thermoplastic resinous materials of high density and crystallinity.

One object of our invention is to provide new catalytic systems which are effective for the preparation of thermoplastic, highly crystalline resins from ethylene and/ or other normally gaseous n-alkenes. Another object is to provide new methods for the preparation of polymerization` catalysts. Yet another object is to provide new processes for the polymerization of ethylenepalone or .with comonomers, to produce thermoplastic resins of high molecular weight and a ydensity (Z4/4 C.) of at least about 0.960. A further object is to provide processes ,for the polymerization of ethylene and the like in which `only-inorganic catalyst-forming materials are charged. ',I'hese and other objects of our invention willbecome apparent from the ensuing description thereof.

The polymerization `of ethylene or other normally gaseous n-alkenes can be effected, in accordance with our invention, at substantial and'commercially attractive rates, at low temperatures and moderate pressures by contacting the ethylene or other alkene charging stock with a ,completely inorganic compound of a transition metal selected from groups 4, 5, 6 and the fourth series of group 8 of the periodic system and an ionizing radiation in a dose having an energy equivalent to 104 to l0'7 REP.

The said transition metal compound is preferably a salt, preferably a halide, such as chloride. It is advantageous to use'a transition metal salt having essentially covalent characteristics, being therefore soluble in liquid ethylene 'or charging stock containing the same, for example, a solution of ethylene in a substantially inert hydrocarbon such as an aliphatic hydrocarbon. v While the invention will be described in most detail with respect to ethylene polymerization, it will be understood that it can likewise be applied to the polymerization of propylene or butylenes; such modification of specific opproduce optimal results are well within the skill of the art..

It should be understood, however, that all gaseous nalkenes are not precise equivalents for the purposes of our invention, which in its preferred embodiment is applied to the polymerization of ethylene, especially the homopolymerization of ethylene. Also, the transition metal compounds employed for the purposes of our invention are not precisely equivalent to each other in operating eiciency and otherwise. In its preferred embodimentyour invention-is applied through the use of halide salts of transition metals of group 4 of the `periodicsystem, especially TiCl2, TiCl3 and/orTiCl4. l The homoor hetero-polymerization of ethyleneY or othergnormally `gaseous alkenes can be `effected over an .metallic compounds with various transition metal salts ,(no radiation) has led to polyethylene resins having a .maximum density of about 0.955 and, in practice, has `suifered the enormous disadvantages of the extreme cost of `organometallic derivatives and the serious hazards infvolved in handling such extremely reactive and pyrophoric materials on an industrial scale.

S lThis invention provides a facile method for the polymerization of ethylene to thermoplastic resins which can be readily Worked on available or slightly modied comf ,rnercial plastic machines, especially to resins having a .density (Z4/4 C.) of 0.960 or more, which is associated with the properties of high crystallinity, excellent low temperature. flexibility, low sWellability in organic solvents,

low permeability to moisture and other vapors, extreme toughness, high tensile strength, high tear resistance, etc. It should be understood that this invention is not concerned with preparation of cross-linked resins or resins of an essentially thermosetting nature, which are stili, rigid, brittle and essentially non-extensible (of the order of 10% or less at ordinary temperatures) such `as have heretofore been produced by exposing conventional poly- `ethylene resins to high energy X-rays or the like.

The process of the present invention can be used to prepare ethylene polymers, propylene polymers, butene polymers and ethylene-propylene copolymers, etc., of widely variant molecular weight ranges and attendant physical and mechanical properties, dependent upon the selection of operating conditions. The inventive process is characterized by extreme flexibility both as regards operating conditions and as regards the products producible thereby. Thus the present process can be effected over extremely broad ranges of temperature and pressure. The practice of the present process can lead to tough, resinous ethylene homopolymers having an approximate specic viscosity (X105) of 10,000 to more than 300,000 [(71 relative -l) 105]. By the term Etough, resinous polyethylene, we mean a polymer having a brittle point below 50 C. (A.S.T.M. Method D746'-51T) impact strength greater than two foot pounds soY per inch of notch (A.S.T.M. Method D256-47T-Izod machine) and minimum elongation at break, at room temperature (25 C.), of 100%.

In a preferred form, the process of the present invention can be used to produce polyethylenes having melt viscosities in the range of to l07 poises at 145A` C; and-densities (Z4/4 C.) `of 0.96 to almost 0.98, being tough, resinous, thermoplastic materials. 1

In what follows, our invention will be descriped in more detail with particular reference to the accompanying Figure and illustrative speciiic examples thereof. 'l The charging stock for the present polymerization process preferably Vcomprises essentially ethylene and/or another normally gaseous n-alkene, particularly terminal l vinyl-alkenes.'l`he alkene charging stocks may contain hydrogen and hydrocarbons, as in renery gas streams, for example, methane, ethane, propane, butanes, etc. However, it is usually preferred to employ as pure and concentrated alkene charging stocks as it is possible to c'ibt'ain.V When' the charging stock contains propylene as wellv as ethylene, both these oleiins may contribute to the production of resinous, higrr molecular weight products.

It is generally desirable to minimize or avoid thev introduction of oxygen, carbon dioxide, water or sulfur compounds into the polymerization system.V Y l Binary or more complex mixtures of the alkenes'can be charged to the process of our invention or the individual alkenes can be charged with co-monomers such as acetylene, butadiene, isoprene, styrene and the like, usually in proportions between' about l and about 25% by weight, basedv on the weight of alkenes. p

In accordance with this invention, depending on the conditions of temperature and pressure and the presence or absence of an added hydrocarbon diluent, ethylene or other alkene charging stock can be polymerized from the gas phase or the liquid phase or in solution in a hydrocarbon diluent. Thus, in the absence of a hydrocarbon diluent and at temperatures above its critical temperature, ethylene or other alkene charging stock can be polymerized as a gas. Even in the absence of a hydrocarbon diluent, liquid ethylene, propylene or I-butene can 'be polymeri'zed at temperatures below the critical temperature under a pressure sufficient to maintain the liquid phase. Even at temperatures above the critical, ethylene or other alkene can be polymerized as a solution, for example, of the order of about 2 to 20% by weight (based on the weight of ethylene or other alkene plus hydrocarbon diluent) under a pressure sutiicient to maintain the desired concentration of alkene in said" solution. The maintenance of suitable phase relationships, as desired,` is a matter merely of chemical engineering well within the skill of those working in the art. Suitable aliphatic hydrocarbon diluents or liquid reaction media are set forth in Alex Zletz U. S. Patent 2,692,257, column 8.lines 52 ff. We can employ saturated hydrocarbon diluents such as n-pentane, isopentane, hexanes, heptanes, octanes, nonanes, decanes, etc.; cycloalkanes such as cyclohexane, cyclopentane, alkylcyclohexanes, etc.; olens such as octenes, dodecenes, etc., especially non-terminal olens. The Iliquid hydrocarbon diluent can be treated to remove ntained oxygen, Water, CO2, etc. by known methods, for example, the method described in Edmund Field and Morris Feller, U. S. Patent 2,691,647, column 9, lines 4 ff.

A Wide variety of completely inorganic compounds of transition metals selected from the groups aforesaid can be used for the purposes vof our invention, being specifically compounds of Ti, Zr, Hf, Th, V, Nb, Ta, U, Cr, Mo, W, Mn, Fe, Co, Ni or mixtures thereof. In general, we prefer to employ salts of these metals derived from various mineral acids, for example, the hydrohalogen acids; oxyhalides, e.g., titanyl chloride or vanadyl chloride and the like; salts of acids of phosphorus, sulfur, nitrogen, etc.` We may also use the specified metal cyanides, cyanates, isocyanates, thiocyanates, isothiocyanates carbonyls, azides, etc. The salts of carboxylic or sulfonic acids may also be used, e. g. titanium `dichloride diacetate. Also, we may use metal derivatives, classiiied herein as salts, having the formula M(OR), wherein M represents the polyvalent metal, R is an alkyl or aryl radical, and n is the valence of M, for example, Ti(OC2H5)4, Ti(OC3H7)4, Ti(OC4H9)4, tetra-Z-ethylhexyl titanate, tetrastearyl titanate, tetraphenyl zirconate and the like, for example, the metal derivatives of the enol forms of acetylacetone, acetoacetic ester and the like.

We particularly prefer Ithe use the transition metal halide catalysts, especially those of titanium, e.g. TiCl4, TC13, TBIIL, TiBfg, TiI4, Btc.

The transition metal catalyst can be supported on various solid materials, such as carbon, silica, alumina, bauxite, fluorided alumina, synthetic or natural aluminosilicates, magnesia, titania, zirconia, powdered aluminum uoride, sodium fluoride, sodium chloride, cryolite or the like. The supported catalysts can be prepared by known methods, which do not form'part of the present invention. Usually the supporting material comprises at least 50 and up to about 99 percent by weight of the total catalyst composition.

It will be understood that for purposes of our invention, a completely inorganic salt of a transition metal is one in which there is no direct bond between a hydrocarbon radical (or substituted hydrocarbon radical) and the metal in question, for example, as in bis-phenyl titanium butylate or the like.

The transition metal salt or other compound should contain said metal in a valence ranging from its maximum positive valence to some intermediate valence state which will not be reduced to metal under the radiation conditions. TiCl4 and TiCl3 are generally advantageous for use in the process of the present invention.

The Weight ratio of the transition metal compound to monomer or mixture of monomers is not critical and can be varied broadly over a wide range. Thus the metal compound may be used in proportions ranging from about 0.001 to about l0% by weight, for example, about 0.1 to about 5 w. percent, based on monomer(s); however, even higher concentrations of said metal compounds, based on monomer(s) can be used in some instances.

An important aspect of our invention is the radiation dose, which is here expressed inREP (Roentgen equivalent physical, being equivalent to`93 ergs per g. of absorber). In order to effectuate the purposes of our invention, hereinbefore stated, the dose should fall within the range of l0El to lO'pREP. This dose may be imparted to the feed stock in one pass or in a series of passes through the radiation and catalysis zone. The rate of dosage is not critical and can be varied over a broad range of about l to about lOkilo REP per hour, more often falling within therange of about l0 to about 104 kilo REP per hour.

Various ionizing radiations can be employed for the purposes of our invention, for example, gamma-l or X-rays, beta-rays (high speed electrons) and various densely ionizingV particles such as neutrons, protons', deu'- terons,I alpha particles, etc. v

Various reactors or Isources of ionizing radiations suitable for practicing the present invention are well known and can be applied as such' or with suitable modifications (for temperature control, pr essure control, pumping of catalyst and reactants, etc.) for the purposesof the present invention. Suitable sources of ionizing radiations include, for example, high energy particle accelera'- tors, nuclear reactors and radioactive isotopes. High energy neutrons can be obtained in nuclear reactors or' from othery sources. HighV energy electrons (0.5 mev. to as as 20 mev.) can be derived from Van de Graaff generators, resonant transformers and linear accelerators. The latter twovaccelerate only electrons, while the Van de Graaff generator can also accelerate positive ions. Suit'- able radioisotopes can beA used in practicing our invention', for example, a high curie Co-60 source, Cs'-'l37 or the like.

yThe process of the present invention is distinguished from many of the known processes for the polymerization of ethylene in being readily operable over an extremely broad temperature range, extending vfrom about -100 to about 250 C. More often operations are conducted at temperatures between about 20 C. and about 80 C.

The polymerization reactions of this invention can be effected' over a broad range of pressures. Suitable pressures will be selected to maintain a desired concentration of ethylene or other feed stock in a given solvent ata given temperature and otherwise to govern phase relationships within the reaction zone, as will be Well understood by those skilled in the art of chemical engineering. Actually, polymerization' can be conducted at pressures ranging from one atmosphere or even less up to the maximum pressure which the selected reaction equipment can .ifi

vwithstand, for example, 30,000 p.s.i. or even more. A s convenient pressure range is about v to 1000 p.s.i.a.

We have observed that the salts of transition metals fare partiallyreduced Vand insolubilized in the solvent in tle 'polymerzationwreaction zone, and are thus incorporated within the r'esinous polymer which is produced.

, 'Iheremoval ofsvarious,inorganicl ash-like materials 3Vfrom, re'sinous polyethylenes is well known in the art. `Thuspolyethylene` or` ethylene copolymer in solution (abtnjti-1A 'Lto .110, W., percent concentration) in a hydrocarlhon' diluent'containing also a solid inorganic catalyst can be vfiltered orcentrifuged` and then treated with polymer precipitants or antisolvents, such as the various alcohols,

"ketoncssuch as acetone or lthe like, etc. Precipitates of `polymers'containing some of the inorganic catalyst can f then besubjected to acid or alkali extraction to remove the inorganic catalyst components therefrom. An alterna- Itive technique is to redissolve the polymer in a suitable `solvent suchfasv boiling `xylenes, thereby leaving inorganic components in a separable form out of solution. These andothertechniques are well known in the art of purifyethylene'polymers containing inorganic residues and `do"fnot constitute part` of the present invention.

4liefoll'owing examples are offered to illustrate our inyentionwithout the ,intentof thereby unduly limiting the ExampleV 41 Th''i'reactor was fa castiron sausage bomb having a capacity 'of Vabout 22 cubic inches (360 cc.). It was charged with 150 ml. n-heptane which had been dried with calcium hydride, said n-heptane containing in solutionA cc. or 0,86 gfof TiCl4 (Bakers C.P. grade). Puriedlethylene was pressured into the'bomb in the amount of g. Ifhe bomb was then sealed and placed in a .Waterproof-container of thin` aluminum. The resultant assembly was centrally placed between 4 spent uranium fuel slgs (Agonnehigh gamma source). The assembly was slowly rotated during irradiation (ilux, 104 r./min.) 've'ra` periodl of 1000 minutes, resulting ina total dosage of 1x107 REP per g. ethylene. The temperature during radiatin-varied'between about 78 and about 95,91?. and the initial pressure was 290 p.s.i.g. Because of the slow tarte-fof""rotationy very poor Amixing was obtained in the bomb. A-fvterirrdiation, the bomb was vented at room temperaturedown to atmospheric pressure and methanol was.` added to the contents to precipitate the ethylene polymerk-" The precipita'ted' polymer jwas filtered and washed 'v /itl'ifconcetrated Aaqueous hydrochloric acid to effect selective solution of TiCla therefrom. (TiC13 was determined bytitrationf With ferric ammonium sulfate, using ammonium thiocyanate indicator.) A clean white polymer was obtained in the amount of 7.2 g.; the yield of polyethylenerecovered was Vtherefore 36 w. percent, based on rcharge.l It was found that this polyethylene had a' densityf(24/4C.) -of 0.961 and` a melt viscosity at 145 C. of 1X 105 poises (method of Dienes and Klemm, I. Applied Physics 17458471 (1946)). The polymer had a melt pointV of :128 C. (temperature at which crystallinity disappear'sfwhen the sample is viewed through crossed Nicol prisms). An kX-ray diagram of the polymer indicated a crystallinity of 83%.,

In a control run in: which no TiClg= was employed, the yield of polyethylene was 11 w. percent, based on charge, and the polymer was a` low molecular-weight material having a specific viscosity'A 105 of 2100 measured at a concentration of 0.125 g. in 100 ml. boiling xylenes.

It will be understood that in lieu of the irradiation soce employed in' the example, one could employ a Van de Graai electrostatic generator, C060, Cs13'I or other radiation sources.

Example 2 This operation was generally similar to Example 1 but the total dose was 5 X 106 REP, or one-half the dose Lused in Example 1. The sausage bomb was charged with 300ml. of pure. dry, heptane containing 0.86 g. TiCb, and about 20 g. ethylene (initial pressure of 290 p.s.i.g. at 25 C.) and irradiated in the same nuclear reactor at about .,F. The reaction'mixture was worked up as in Examplel and 0.9 g. of resinous polyethylenes were obtained. This polymer had a density (Z4/4 C.) exceeding 0.97 and a melt viscosity at C. of 8.6)(104 poises. y v

' Example 3 This operation was generally similar to Example l but 0.9 g. of TiCl3 was substituted for the TiCl4 of Example 1. The initial pressure of ethylene in the bomb was 280 and the final pressure was 150 p.s.i.g. The radiation rate Was 3.6 104 r./minute and the total dose was 10I REP. The products were worked up as in Example l to yield 7.8 g. of solid polyethylenes insoluble in hot n-heptane land a trace of heptane-soluble polymer. The heptaneinsoluble polymer had a melting point of 128 C., d (24/ 4 C.) of 0.9608Aand melt viscosity of 4 l06 poises. When the processywas repeated but the radiation was increased by a factor of 10, the polyethylene yield only doubled, but the melting point dropped sharply to 121 C. and th density vto 0.9517.

` `Example 4 p When propylene is subjected to the same inorganic compounds and irradiation as have been described above in connection with ethylene polymerization, somewhat lower conversions (compared to ethylene) are obtained `to produce normally solid polymers, together with normally liquid polypropylenes. s

Y Example 5 A catalyst of 0.5 g. TiCl.,E impregnated on 20 g. of an activated gamma-alumina gel was added to a V250 ml. Magne-Dash reactor containing ml. of pure, dry nheptane and the mixture was pressured with ethylene to 410 p.s.i; at 25 C.` The contents of the reactor were magneticallystirred and exposed at 25 C. to a Co-60 source for a total dosage of 10rz REP at the rate of 0.6X104 r; per minute. The final ethylene pressure in the reactor was p.s.i. The reactor contents were worked up as before to yield 10.2 g. of heptane-insoluble polymer and V0.5 g. of heptane-soluble polymer. The melt viscosity of this polymer at 145 C. was 104 poises. The density was 0.974 (Z4/4 C.). The accompanying gure illustrates a continuous method for practicing the process of the present invention. Numerous obvious chemical engineering details, such as pumps, valves, etc. have been omitted in the interests of simplification. Y The ethylene 'or other alkene charging stock is charged to the process through line 10 into the lower portion of an absorption tower 11. An aliphatic solvent, particularly a normally liquid alkane or cycloalkane, is introduced into the upper portion ofthe absorption tower through line 12. Unabsorbed residual gases such as hydrogen and normally gaseous alkanes are withdrawn from the upper portion of tower 11 through line 13 and a 2-10 w. percent solution of alkene in the solvent is withdrawn from the lower end of the absorption tower through line 14. Catalyst is added to the stream in line 14 through line 15. Thus, a dilute solution of TiCl4 in a saturated or other aliphatic hydrocarbon can be introduced into line 15; if desired, finely dispersed TiClB or TiCl2 in an aliphatic hydrocarbon medium can be used instead. The metal halide can be used in proportions of about 0.01 to about 5 percent by weight, based on alkene charging stock. The mixture ows `thence through a heater 16 wherein its temperature is adjusted to a desired value, usually between about 20 C. and about 200 C., thence through suitable radiation shielding 17 into a reactor 18. The reactor is preferably provided with a suitable stirring mechanism to insure adequate contacting of the alkene c7 feed* stockJ with catalyst; good Vheat transfer, ef@- nie-.ionizng radiation source- Qf tubular fm; 19;. .S schematically'illustrated. It is obviousthat 'manllmodl' lications can bi'emade ofthis detail; for example, the

radiation source'may* beplaced within'the reactor: The radiationsourcecan be spent uraniuml fuel slugs,V radioactive'cobalt; radioactive cesium', a` Vande Graai'aca celerator," etc; Y

The residence time of the catalysts and reactants* in reactor 18 is adjusted to provideffor the accumulation of a suitable radiation dose in the reactor contents ineither a singlepassi orv inv multipleV pass operations.` The reaction mixture is withdrawn from reactor18and shielding 17 'through line 20, whence atleast a' portionthereof canbediverted' through line 21' andrecycledto; the reactor for multiple pass operationsi The net eent ispassed' from lineu 20"through' a heater or' cooler Z2 adapte'dftolcontrol'the temperature ofthe reaction-mixture to'a suitable level forsubsequent treatments.

I'fdesired, an additional portion of'solvent forthe normally solidpolymer can be introduced A'through line into li'ne 20.'. The contents ofline 20" are discharged into a catalys't'separation zone. Thus the-solidV polymer solution at a' concentration lof between about 10.11 and Y about weight percent in an aliphatic hydrocarbon solvent'(con` taining normally solid catalystresidues) can be charged into'. separator 24, whichI cantak'eitheffornlofiaflter, centrifuge: or other equipment lhaving.-,sin'i'ilarf function; Preferably'thetemperature of 'the str'ea'm charged to vessel 24 is betweenabout 85 C.I and' aboutf150 C;- andthe streamlis under sumcient pressureto. maintainth'e liquid phase. When a filter is used, it isf desirable-1 toil use-the conventional filter aids suchv as clays, diatomaceous earths, mixtures ofV carbon black and acid-treated clays.: Catalyst residue is withdrawn from separator 24. through line Z5l andA liquid effluent is 1passed, through` line. 26 into acooler 27 to lower the temperature toy therpoint where normally solid polymer becomes :substantially-insolubilizedin the hydrocarbon medium, usuallya temperature between about 20 and 50 C.. The cooledcontents of line Z6 are then passed into-'a vessell 28 which can be a lter, centrifuge or the like frthe separation of solid polymer from solvent medium.- Thesolventvis withdrawn through line 29 andthe solid v-polymerv at 30. The solvent can be recycled for useinthe process;V The polymer product can be treatedfurther toremove-residual solvent, traces of polyvalent metal halide catalyst,.etc. The polymers produced bythe process of this invention can be subjected'to such after-treatment asmay bedesired Vto it them for particular uses or to impart desired properties. Thus, the polymers can be extruded, me-` chanically milled, filmed orcast, or-convertedtosponges or`latices. Antioxidants, stabilizers, lillers, extenders, plasticizers, pigments, insecticides, fungicides, etc.v can be incorporated in the polyethylene and/ ori-in: by-productl alkyla'tes or rgreasesf The polyethylenesmay belemployed as coating materials, binders, etc; to-evenfawider extent than polyethylenes made by. prior processes.

The polymers produced by the-process Aof-.the presentY invention, especially the polymers having high specific viscosities, can be blended with olen resins derived from? other processes to impart stiiness or other desired properties thereto. The solid resinous product producedfby theprocessof the present invention can, likewise, be blended in any desired proportions with hydrocarbon oils, ,waxes such as parain or petroleum waxes, with ester waxes,

with'V high molecular weight polybutylenes and with other' organic materials. Small proportions between about -0l and'about l percent of the various polymers.ofgethylenev 8 produced by, 'the' process ofthe present` invention" canf be dissolvedio'r dispersed 'i n hydrocarbon lubricating 'oils to increaseVI an'dto'de'crease oili'con'sumptioii'when the compoundedv 'oils are employedfinhrotors larger 'amounts of vpolyethylen'es may becompounddwith oilsiofvarious kin'dsand forvarious purposes.v

The'productshaving `aV molecular weight Vof`-50,0'0O or more produced 'byV the present'inven'tion', ca'n beemployed in small proportionsto substantially' increase thviscosity ofuent liquid hydrocarbon oilsv and as gellingfagents for such oils. f

The polymers 'produced by tlepr'esntprocess can be subjected' to'chem'ical modifying treatments', su'ch` as halog'enation', halogenation' followcdby dehalogenatiomsul? fohalogenation by treatment with sulfryl chloride, sul'- fonation, and other reactions to which lydrocarbonsn'ly be subjected.

Having thus dscribed'ou'r invention, whatwe clairnis:

l. A process'for' the polymerization of ta normallil gaseous'n-alkene 'to produce la normally solid Ythermoplastic' polymer, which processn comprises contacting, said alkenewith-a'` catalytic system consisting, essentially off-a compound `of`a transition rretal lselected from., the group consisting/of'titanium',` zirconium and hafnium vand having no metal to "hydrocarbon radicalb'on'd and`au ionizing radiation dose in the range of about 104 to 107 REP, and recovering a polymer thus'produced.

2. The process of claim l-wherein said compound is a salt 3.I The process of claim 1 wherein said dose isin-the range of about 10to 10"REP. f

The processcf claim 3 'wherein said -contactingais effected at at'emperature between about 20 C. and about 804 C. l

5.A The process of claimrl wherein said-- alkenefis ethylene.. l f

6.k The process of claim- 1 wherein saidA alkenefd is propylene. y

7.` The process of claim-1-whereinisaidradiation-is gamma radiation. l p

8l The process of Rclaim. l` whereinsaid-radiation-is beta radiation.

9`. A process which` consists essentially.- of contacting ethylene with a halide of titanium andan ionizing radia-I' tion dose withinY the range of about 1,0% to- 10'I REP att atemperaturenot inA excess-of about 2505 C.I andtatsuperatmospheric pressurenot -inA excess ofra'bout--l000-p.s.ita;; and-separating a' normally solid polymer fromV ethylene having a density (Z4/4 C.) ofvat least0t96`and aanelt1 viscosity at C. of-atleast 105 poises;

10. The process of claim Y9-wherein-saidtitaniumhalide. isfa= titanium chloride. v

11. The process vof-.claim 10-whereinsaid titanium chloride is titanium tetrachloride..

12. The process of claimt10fwherensaid"titailiullll chloride is Vtitanium trichloridef References cited 'inthe fue'. ofihspatent. UNITED-STATES PATENTS:

2,437,531 Harmanl l Maf: 911.1948 FOREIGN PATins'rrs`` 714,843 GrearBn'tain annsepr.: 1;- 19521- OTILER REFERENCES" c Bretton et al.: N.Y.O. 3309,1Progress'ReportwNowZa rst-quarter 0952). Y.- J l y l. v

Ellis et al.: The Chemical Actionof.1UltravioletRays.; New Yorkt(l941),.pp. .409411.A n I v g 

1. A PROCESS FOR TH EPOLYMERIZATION OF A NORMALLY GASEOUS N-ALKENE TO PRODUCE A NORMALLY SOLID TERMOPLASTIC POLYMER, WHICH PROCESS COMPRISES CONTACTING SAID ALKENE WITH A CATALYTIC SYSTEM CONSITING ESSENTIALLY OF A COMPOUND OF A TRANSITION METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM AND HAFNIUM AND HAVING NO METAL TO HYDROCARBON RADICAL BOND AND AN IONIZING RADIATION DOSE IN THE RANGE OF ABOUT 104 TO 107 REP, AND RECOVERING A POLYMER THUS PRODUCED. 